Can Your Microbiome Reveal Your Ideal Diet?

Forget carbs and calories. Your microbiome may hold the key to better blood sugar control

Faecalibacterium prausnitzii bacteria, illustration. This is one of the most abundant bacterial species found in the human gut.

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For those with diabetes or prediabetes, managing blood sugar levels is a critically important part of preventing the progression of this disease and avoiding serious complications. But even for healthy people, keeping your blood sugar in a healthy range can help reduce the risk of obesity and the risk of developing diabetes.

How do you avoid high blood sugar?


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Up until recently, advice for managing your blood sugar has focused on the nutritional composition of foods. Specifically, you’re advised to pay attention to the quantity and quality of carbohydrates in your diet.

Tracking quantity is pretty straight-forward: you simply count grams of carbohydrates. Assessing the quality of the carbohydrates in your diet gets a little more nuanced. You might take into account how much sugar or fiber a food contains, for example.

The problem is that two different foods with the same amount of carbohydrate or sugar or fiber can still produce very different glycemic responses. A white potato, for example, might have the same amount of carbohydrate and fiber as a serving of white pasta. But the potato is likely to cause a higher spike in blood sugar.

Is Glycemic Index more important than carbs?

This was the problem that the glycemic index hoped to solve, by attempting to factor in the variable known as the human digestive process. Researchers fed human volunteers all kinds of different foods and measured their blood sugar levels. They used this data to produce the Glycemic Index, which represents the average rise in blood sugar in response to various foods. As a final step, multiplying the Glycemic Index of a food by the amount of carbohydrate in the serving gives you the Glycemic Load, which is a measure of both quality and quantity.

For decades now, our best tools for managing blood sugar have been counting carbs or glycemic load. And studies have shown both to be moderately effective in controlling blood sugar and improving outcomes in people with or at risk of diabetes.

But there was still a big problem. The Glycemic Index of a food represents the average blood response to that food among all the individuals tested. But If you dig into the data, you’ll see that those averages represent a very wide range of individual responses. The Glycemic Index of a food might be 58, but the range of individual responses included in that average might be 47 to 69.

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